The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Internal combustion engines combust a fuel and air mixture to produce drive torque. More specifically, air is drawn into the engine through a throttle. The air is mixed with fuel and the air and fuel mixture is compressed within a cylinder using a piston. The air and fuel mixture is combusted within the cylinder to reciprocally drive the piston within the cylinder, which in turn rotationally drives a crankshaft of the engine.
Engine operation is regulated based on several parameters including, but not limited to, intake air temperature (IAT), manifold absolute pressure (MAP), throttle position (TPS) and engine RPM. With specific reference to the throttle, the state parameters (e.g., air temperature and pressure) before the throttle are good references that can be used for engine control and diagnostic. For example, proper functioning of the throttle can be monitored by calculating the flow through the throttle for a given throttle position and then comparing the calculated air flow to a measured or actual air flow. As a result, the total or stagnation air pressure before the throttle (i.e., the pre-throttle air pressure) is critical to accurately calculate the flow through the throttle. Alternatively, the total pressure and/or static pressure can be used to monitor air filter over-restriction.
An air filter is often used in an internal combustion engine to remove contamination from the induction air. Over a period of use the air filter can become plugged and over-restrict the air flow into the engine. Other factors can affect the air flow through the throttle such as, for example, the air intake becoming plugged by dirt or a foreign substance or object, which can also result in an over-restricted air flow condition. The over-restricted air flow condition can reduce performance, reduce fuel economy and increase engine emissions. Therefore, it is important to determine whether air flow is over-restricted.